Posted
by
Unknown Lamer
on Monday September 24, 2012 @05:40PM
from the fog-from-insufficient-rendering-power dept.

New submitter kelk1 writes "If the size and mass of this gas halo is confirmed, it also could be an explanation for what is known as the 'missing baryon' problem for the galaxy [...] a census of the baryons present in stars and gas in our galaxy and nearby galaxies shows at least half the baryons are unaccounted for [...] Although there are uncertainties, the work by Gupta and colleagues provides the best evidence yet that the galaxy's missing baryons have been hiding in a halo of million-kelvin gas that envelopes the galaxy."

These insignificant lumps came together to form the first union, our sun, the heating system. And about this glowing gas bag, rotated the Earth, a cat's eye among aggies, blinking in astonishment across the face of time.

Well, we were covered with a molten scum of rocks, bobbing on the surface like rats. Later, when there was less heat, these giant rock groups settled down among the land masses. During this extinct time, our Earth was like a steam room, and no one, not even man, could get in. However, the oceans and the sewers were simmering with a rich protein stew, and the mountains moved in to surround and protect them. They didn't know then that living as we know it was already taking over.

Animals without backbones hid from each other, or fell down. Clamosaurs and oysterettes appeared as appetizers. Then came the sponges, which sucked up about 10% of all life. Hundreds of years later, in the Late Devouring Period, fish became obnoxious. Trailerbites, chiggerbites, and muskquitoes collided aimlessly in the dense gas. Finally, tiny, edible plants sprang up in rows, giving birth to generations of insecticides and other small, dying creatures.

Millions of months passed, and, 28 days later, the moon appeared. This small change was reflected best, perhaps, in the sand dollar, which shrank to almost nothing at the bottom of the pool, where even dumb amphibians like catfish laid their eggs in the boiling waters, only to be gobbled up every three minutes by the giant sea orphans and jungle bunnies, which scared everybody. And so, IN FEAR AND HOT WATER, MAN IS BORN!!!

here in the technical vastness of The Future, we can guess that surely, the past was very different. We know for certain, for instance, that for some reason, for some time in the beginning, there were hot lumps. Cold and lonely, they whirled noiselessly through the black holes of space.

This is making me feel like there's a big game going on.

You'll never escape gravity!

OK, you escaped gravity, but you'll never survive the Van Allen Radiation Belt!

OK, you passed through the Van Allen Radiation Belt, but you'll never make it through the Asteroid belt!

OK, you successfully navigated the Asteroid belt, but you'll never make it through the Kuiper belt!

Dang, you made it through the Kuiper belt, but you'll never, ever make it through the Baryon Halo! Muah ha ha ha haaaah!

Even with the speed of light broken, the Galaxy is still very very very big.

100,000 Light years Diameter. From my understanding the Theoretical model says we can probably go 10x the speed of light. Meaning that it will still take 10,000 years at 10x speed of light. Heck if you use the Speed of Plot that Star Trek and other Sci-Fi uses, it still takes about 100 years just to cross the galaxy.

Just to give you an idea of size. Star Trek Seems Warp drive seems to have an average of 1000x the speed of light. t

Alright. First off, go take a course in modern physics. Then you'll understand the concept of time-space better. As velocity of an object, let's say a spacecraft, increases time slows down for occupants of the object. This phenomenon has been tested and proven with the retired Blackbird spy plane. So, if you could travel at 10x the speed of light it wouldn't take 10,000 years to cross 100,000 LY of space, and I have doubts anything like that is possible, in this lifetime. I'm aware of the theories, and how

Depends on how dense it is. If you immerse yourself in water at 100C (boiling point for you imperial scumdogs:) you won't last long at all, but in dry air at 100C you can survive for substantially longer. If the gas was so sparse that you might only hit a molecule every few seconds or so then the temperature might not matter so much. The article hints that the density is low "The estimated density of this halo is so low that similar halos around other galaxies would have escaped detection." but that doesn't really help in absolute terms.

(or maybe you're making a joke... i don't get the reference in the first line you posted)

"... a few hundred times hotter than the surface of the sun." That's very warm.

It's relative warmth in the 100,000 K and up club it's rather difficult to keep track because once you've boiled away Tungsten, there's not much meaning in additional units of heat.

It does give me the impression the galaxy is actually protecting us from all this hot matter, it gets too close and gets blown away by a star or attacted to cooler matter. I imagine, however, this halo should be generating some serious amounts of IR. Need that ol' James Webb telescope to explain more about it.

The key is how undense it is. When a physicist talks about "temperature" in this context it's just short-hand for "average velocity"... it doesn't necessarily imply thermal equilibrium, even. So 1e6K means a high average velocity. Now, if it were a dense gas there might be collisions that would do things like excite electrons into higher states, which would then decay by emitting photons (light), and so the gas would lose thermal-kinetic energy over time.

In a sufficiently diffuse gas, loss processes like this are very slow because the chances of collision are very slow, so it can stay "hot" (that is, have a high average velocity) for a long, long time.

Temperature (in Kelvin) is actually more useful in astrophysics and thermodynamics of plasmas. It wraps up a bunch of messy real world constants into one number, and also neatly describes the behavior of the volume of gas as a whole, rather than forcing the analyst to perform a lot of messy integrating and averaging of distributions of actual velocities in three dimensions.

Think about it this way. No one is really interested in how fast a specific particle is moving. They're more interested in how the Thermal Energy of the gas couples with other systems.

A galactic halo would be coupled very, very, (very^18) poorly with other systems, at least conductively. And probably even worse convectively, given the scales involved. Radiatively, I don't know near enough about the behavior of these particles to talk about why, but if it's stayed that hot for the life of the universe, effectivelt, then apparently its either not coupled to another system, coupled far more strongly to itself than anything else, or somehow not stimulated to emit blackbody radiation... or all three of the above.

On the other hand Temperature (e.g., in Kelvin) is only marginally useful in describing the distribution of a phenomena that isn't in thermal equilibrium (say non-blackbody radiation)...

For example, people used to grade lightbulbs by their color Temperature, but that didn't say much about the quality of illumination from said lightbulb. Now they use CRI (color rendering index) for lightbulbs which give some information about the actual distribution instead of the really poor assumption that the illuminatio

I don't think it has been this hot for the entire life of the universe - it actually hot hotter with time most likely. This was likely gas found in intergalactic space that fell gravitationally towards the milky way. After falling for billions of years it is moving really fast. However, the gas is so sparse that there really aren't any collisions to speak of. Sure, if a particle hits a star or planet or something that will stop it, but chances are this stuff is hitting our atmosphere all the time, but f

Temperature is in a way a measure of the energy in the system to be used to excite particles into higher energy states. In that way it incorporates several different forms of energy that are distributed "randomly" meaning they don't have a general direction of travel but none the less will provoke particles on the scale of atoms to move outside of their current stable equilibrium.

When a physicist talks about "temperature" in this context it's just short-hand for "average velocity"... it doesn't necessarily imply thermal equilibrium, even. So 1e6K means a high average velocity. Now, if it were a dense gas there might be collisions that would do things like excite electrons into higher states, which would then decay by emitting photons (light), and so the gas would lose thermal-kinetic energy over time.
In a sufficiently diffuse gas, loss processes like this are very slow because the chances of collision are very slow, so it can stay "hot" (that is, have a high average velocity) for a long, long time.

Uh, no. If the collision rate weren't high enough to excite electrons into higher states, it wouldn't be radiating X-rays, which is how Chandra detects the gas. Not a whole lot is known about gas in halos like the Milky Way's, but clusters have been extensively studied, and the gas is pretty close to thermal equilibrium [caltech.edu], but not exactly. Hot cluster halos are ubiquitous, and it's not terribly surprising that more isolated galaxies have hot halos as well. The gas heats from loss of gravitational potential wh

If the collision rate weren't high enough to excite electrons into higher states, it wouldn't be radiating X-rays, which is how Chandra detects the gas.

Chandra isn't seeing X-ray emissions from the gas, it's seeing X-rays being absorbed by the gas. Specifically, observing 8 X-ray sources hundreds of millions of light-years beyond the gas, it was discovered that some of the X-rays from those sources were being absorbed, and it was possible to deduce the temperature of the absorbing gas.

Chandra isn't seeing X-ray emissions from the gas, it's seeing X-rays being absorbed by the gas. Specifically, observing 8 X-ray sources hundreds of millions of light-years beyond the gas, it was discovered that some of the X-rays from those sources were being absorbed, and it was possible to deduce the temperature of the absorbing gas.

Whoops. My bad, [nasa.gov] But my point still stands: the light is being absorbed by oxygen ions at a temperature of a million Kelvin: what do you think is ionizing them?

When people refer to temperatures in a galactic halo, they absolutely mean to imply that the halo is somewhere close to thermal equilibrium.

Somewhere close to the airspeed velocity of an unladen swallow (European)

Yeah, that's my point. A really hot gas can't be gravitationally bound to the galaxy. It would all fly off into intergalactic space and then you wouldn't have a halo any more. I think what they're doing is regarding "temperature" as a stand-in for DENSITY. It's THIN not HOT.

Yeah, I'm having a few problems with the idea. Temperature actually implies thermal equilibrium, which in turn requires interaction. However, those atoms/molecules are, shall we say cosmicly non-interacting, being so dispersed that they basically form a hard vacuum. There are then a number of problems with the picture. One, why do the molecules not simply fall back into the galaxy (or if you like, why were they pushed out of the galaxy in the first place)? Several billion years accumulation of solar wi

Temperatures of near vacuum gasses are not the same as temperatures of gasses at higher pressures. You can't just stick a thermometer in and see what it reads. What you do is measure the kinetic energy of individual gas particles, and back-calculate to find out what temperature a regular gas would have in order that its average molecule would have the same kinetic energy. In the vacuum of intergalactic space, the individual gas particles can have tremendous kinetic energy, and they are likely to keep th

What you do is measure the kinetic energy of individual gas particles, and back-calculate to find out what temperature a regular gas would have in order that its average molecule would have the same kinetic energy.

It likely only got hotter with time - as it fell towards the galaxy and picked up speed. In order to lose temperature the gas molecules have to actually interact with something. There isn't anything for them to interact with - these things are flying through intergalactic space basically flying around the galaxy.

Put hot water in a thermos and it stays hot for a while. Put hot water in intergalactic space and it stays hot for much longer. However, the water molecules still interact and release photons ou

I'll take you at your word (I'm a chemist, not a particle physicist, though I do know enough about Boltzman distributions that I could probably work it out).

Agreed that the velocity distribution might not be right - initially this stuff all started out as a mostly uniform cloud of gas with particles falling towards the nearest clump of mass, with particles that are farther picking up more speed - should be possible with some assumptions and calculus to work out what the distribution is assuming no collision

Hold on a second... so they just discovered the Galaxy is surrounded by gas that's the same temperature as the surface of the sun, and is 300,000 lightyears across... possibly extending far into other galaxies... I'm going to take a wild stab here and say that, if that's true it probably pervades the entire universe... Isn't this the biggest scientific discovery in the past decade? What effect does this have on Dark Matter, Dark Energy, etc... etc...

Hold on a second... so they just discovered the Galaxy is surrounded by gas that's the same temperature as the surface of the sun, and is 300,000 lightyears across... possibly extending far into other galaxies... I'm going to take a wild stab here and say that, if that's true it probably pervades the entire universe... Isn't this the biggest scientific discovery in the past decade? What effect does this have on Dark Matter, Dark Energy, etc... etc...

It has been known for a long time that the intergalactic medium is hot enough to be ionized [ua.edu]. That part is not news. The thing that's news is that the hot gas makes it possible to account for the baryons in the Milky Way halo, which were previously undetected.

The thing that's news is that the hot gas makes it possible to account for the baryons in the Milky Way halo, which were previously undetected.

The thought that we're just the 0.1% of the dirty precipitate at the bottom of the gravity well is a tad humbling. Not that much isn't when you look up from the T.V. to a clear night sky.

Galaxies are apparently quite dynamic things: a rain of in-falling gas to make new stars, pressure from new stars pushing back, dust build up from all this nucleosynthesis, blackhole cores that cycle on and off. One paper I read even claims this is the beginning of the 'green' period for the Milky Way. The conditions for life will be come more abundant: the number of long-burning dwarf stars like the sun continue to rise as a fraction of the stellar population while the dust percentage (you know, planets) rises at the same time a lot of the big super- and hyper- novae are over with.

However, longer term prospects seem bleak if the dynamic gas is all consumed or blown away. Eventually stellar production would grind to a halt. The green galaxy would give way to white and red dwarfs floating amid other stellar corpses and thinned gas.

I have to wonder if the temperature and environmental coupling of this gas is enough to become a future raw star material resource? I mean, we're talking about 99.9% of the matter here and it's already gravitationally bound. Could someone model long-term in-fall of this ionized matter? Could it cool fast enough or even at all to beat the predicted 'big rip' from dark energy and give the galaxy a 2nd, 3rd, etc. childhood?

As a plasma physicist, I'm not bothered or concerned about them calling it gas. When interacting with the general public to discuss plasma related research, sometimes you find yourself having to make a choice between trying to teach a person what a plasma is, or teaching them what you are doing with it. Attention spans, and time/space are sometimes limited with such interactions and you have to choose your priorities.

Aren't we all supposed to have learned about solid, liquid, gas and plasma back in grade school? I seem to recall having the concept explained over and over again from before high school and right through it. I can see the people who pass through school without learning to read having trouble with it, but it's a depressing thought that the ones who managed to become journalists missed the entire concept.

Although many people do learn that in school, they either don't remember it or never learned anything about what a plasma actually is other than it is some mysterious hot stuff, and can't see how it is pretty similar to gas in a lot of situations.

If anything, I've run into more trouble with people who paid attention to such things in school and not much else. They get stuck with this notion that everything has to be pigeon-holed into one of those categories (which makes it even

Aren't we all supposed to have learned about solid, liquid, gas and plasma back in grade school?

Considering how many comments ON A NERD SITE say "loose" instead of "lose", aliterate things like "there cars are over their" and "The tomato's are in season", I think the fact that they don't know what a plasma is is pretty understandable.

No. The Galactic Barrier is a (fictional) force field around our galaxy, preventing matter to get out or in (supposedly placed there by some higher intelligence).
The real thing is a very sparse cloud of ionized gas. It doesn't work like a barrier at all.

Of course every time a story comes up about missing matter being found, people want to know the impact on the need for dark matter. There is evidence that suggest how much matter in the universe is made out of baryonic matter (protons and neutrons... essentially anything made of atoms), and how much is made out of non-baryonic matter. The latter category is dark matter. In addition to the missing non-baryonic matter, there is also a bunch of missing baryonic matter, which what is being found by studies l

This just accounting for regular own (baryonic) matter. The Halo is still mostly "Dark" matter, which is non-interacting. (It may be WIMPs, i.e., non-baryonic, or it may be quark nuggets, i.e., baryonic, but either way it is non-interacting.)